netdev - Re: [PATCH] BRIDGE: As per 802.1D clause 9.3.4 Added support to prevent processing port's own BPDU (If a loopback condition exists)

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Message-ID: <20110330092542.6344b324@s6510>
Date:	Wed, 30 Mar 2011 09:25:42 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Sasikanth V <sasikanth.v19@...il.com>
Cc:	shemminger@...ux-foundation.org, netdev@...r.kernel.org,
	bridge@...ts.linux-foundation.org
Subject: Re: [PATCH] BRIDGE: As per 802.1D clause 9.3.4 Added support to
 prevent processing port's own BPDU (If a loopback condition exists)

On Wed, 30 Mar 2011 21:03:36 +0530
Sasikanth V <sasikanth.v19@...il.com> wrote:

> 
> Signed-off-by: Sasikanth V <sasikanth.v19@...il.com>
> ---
>  net/bridge/br_private.h   |    1 +
>  net/bridge/br_stp.c       |   20 ++++++++++++++++++--
>  net/bridge/br_stp_if.c    |    2 ++
>  net/bridge/br_stp_timer.c |    1 +
>  4 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
> index 387013d..d9f79dd 100644
> --- a/net/bridge/br_private.h
> +++ b/net/bridge/br_private.h
> @@ -149,6 +149,7 @@ struct net_bridge_port
>  #ifdef CONFIG_NET_POLL_CONTROLLER
>  	struct netpoll			*np;
>  #endif
> +	u8                              is_own_bpdu; /*Port recvd its own BPDU*/
>  };
>  
>  #define br_port_exists(dev) (dev->priv_flags & IFF_BRIDGE_PORT)
> diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
> index 7370d14..491d9c6 100644
> --- a/net/bridge/br_stp.c
> +++ b/net/bridge/br_stp.c
> @@ -107,6 +107,12 @@ static void br_root_selection(struct net_bridge *br)
>  	u16 root_port = 0;
>  
>  	list_for_each_entry(p, &br->port_list, list) {
> +		/*Don't consider the Port for root selection
> +  		  which rx'd its own bpdu because of loopback
> +		  in the bridge
> +  		 */
> +		if (p->is_own_bpdu)
> +			continue;
>  		if (br_should_become_root_port(p, root_port))
>  			root_port = p->port_no;
>  
> @@ -278,8 +284,16 @@ static int br_supersedes_port_info(struct net_bridge_port *p, struct br_config_b
>  	if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
>  		return 1;
>  
> -	if (bpdu->port_id <= p->designated_port)
> +	if (bpdu->port_id <= p->designated_port) {
> +		/*802.1D 9.3.4 Validation of received BPDUs
> + 		 NOTE 1—If the Bridge Identifier and Port Identifier both 
> + 		 match the values that would be transmitted in a Configuration
> +		 BPDU, the BPDU is discarded to prevent processing of the Port’s 
> +		 own BPDUs;*/
> +		if (bpdu->port_id == p->designated_port)
> +			p->is_own_bpdu = 1;
>  		return 1;
> +	}
>  
>  	return 0;
>  }
> @@ -411,7 +425,7 @@ void br_port_state_selection(struct net_bridge *br)
>  			p->config_pending = 0;
>  			p->topology_change_ack = 0;
>  			br_make_forwarding(p);
> -		} else if (br_is_designated_port(p)) {
> +		} else if (!p->is_own_bpdu && br_is_designated_port(p)) {
>  			del_timer(&p->message_age_timer);
>  			br_make_forwarding(p);
>  		} else {
> @@ -446,6 +460,8 @@ void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *b
>  	br = p->br;
>  	was_root = br_is_root_bridge(br);
>  
> +	p->is_own_bpdu = 0;
> +
>  	if (br_supersedes_port_info(p, bpdu)) {
>  		br_record_config_information(p, bpdu);
>  		br_configuration_update(br);
> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
> index 5593f5a..fc4ec63 100644
> --- a/net/bridge/br_stp_if.c
> +++ b/net/bridge/br_stp_if.c
> @@ -37,6 +37,7 @@ void br_init_port(struct net_bridge_port *p)
>  	p->state = BR_STATE_BLOCKING;
>  	p->topology_change_ack = 0;
>  	p->config_pending = 0;
> +	p->is_own_bpdu = 0;
>  }
>  
>  /* called under bridge lock */
> @@ -101,6 +102,7 @@ void br_stp_disable_port(struct net_bridge_port *p)
>  	p->state = BR_STATE_DISABLED;
>  	p->topology_change_ack = 0;
>  	p->config_pending = 0;
> +	p->is_own_bpdu = 0;
>  
>  	del_timer(&p->message_age_timer);
>  	del_timer(&p->forward_delay_timer);
> diff --git a/net/bridge/br_stp_timer.c b/net/bridge/br_stp_timer.c
> index 3e96514..99ea288 100644
> --- a/net/bridge/br_stp_timer.c
> +++ b/net/bridge/br_stp_timer.c
> @@ -67,6 +67,7 @@ static void br_message_age_timer_expired(unsigned long arg)
>  	spin_lock(&br->lock);
>  	if (p->state == BR_STATE_DISABLED)
>  		goto unlock;
> +	p->is_own_bpdu = 0;
>  	was_root = br_is_root_bridge(br);
>  
>  	br_become_designated_port(p);


The idea is valid, but putting state variable per port is an
ugly way to solve it.
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